star matrix is singular

Dear Trnsys users,
I'm trying to perform a sensitivity analysis with Trnsys15-Comis3.1 on
natural night cooling (single sided natural ventilation) in a small office.
Ventilation air by day is mechanically blown into the office and extracted
in the corridor. Using Matlab I can carry out many simulations at once. The
input data change each time for one parameter. The value of the internal
convective heat transfer coefficient depends on the surface (wall vs floor),
the current time (working hour or not) and the presence of the night
ventilation. Night ventilation through louvres in the façade is (manual)
controlled by maximum indoor and outdoor temperature during the last day.
Only changing the height of the zone 'kantoor' (= office) a little bit from
probe123.bui to probe124.bui, and therefore the areas of the internal walls,
causes the next error (see probe124.lst):
***** ERROR ***** TRNSYS ERROR # 185
UNIT 10 TYPE 56 MULTIZONE BUILDING
STAR MATRIX IS SINGULAR - SIMULATION STOPPED.
I tried a lot of things to understand the reason of and find a solution for
this problem (e.g. changing values of convective heat transfer coefficients
and), but couldn't find it. Has any one had the same problem? Or does
somebody know the reason? You can find all the files in attachment.
thanks in advance,
Hilde Breesch
PhD student Buildings & Climatic Control
Ghent University, Department of Architecture & Urban Planning
Plateaustraat 22, B-9000 GENT
tel. +32 9 264 78 61 fax. +32 9 264 41 85
e-mail: Hilde.Breesch@xxxxxxxx
http://allserv.ugent.be/~hbreesch/research